There is known a percussion-rotary drilling tool (cf. SU, A, 284, 918) comprising a body designed to interact with a percussion-rotary device and a casing in the form of a sleeve. The casing accommodates rock-crushing elements representing concentric rings and arranged in a manner allowing axial displacement thereof. Said elements include shanks interacting with the body. The casing comprises means enabling its axial displacement with respect to the body. Both the body and the casing have at least one through channel to pass a working medium used for removing slime from the borehole.
The known tool is suitable for drilling holes in low- and medium-abrasive rock. However, the use of such a tool in highly abrasive rock presents a difficulty for rock-crushing elements wear out rapidly due to a limited length of its wearable portion and absence of requisite means to compensate for wear of said rock-crushing elements, a disadvantage resulting in low durability of the tool.